1. Field of the Invention
The present invention relates to an absorbent article such as disposable diaper, pad for diaper, sanitary napkin, pet sheet and the like. More particularly, the present invention relates to an absorbent body to be used in the absorbent article and a manufacturing process therefor.
2. Description of the Related Art
Generally, absorbent articles are constructed to include: a liquid-permeable topsheet; a liquid-impermeable backsheet; and an absorbent body (absorbent core) interposed between the two sheets. In many cases, the absorbent body is composed of absorbent fibers such as pulp and particulates of absorbent polymer. In case of the absorbent body for use in absorbent article, the improvement of compressive recovery (absorbency) and the improvement of shape stability are important challenge.
Japanese Unexamined Patent Publication (Kokai) No. 2-74254 (74254/1990) discloses an absorbent body which contains 10 to 70% by weight of heat-fusible crimped fibers, 10 to 70% by weight of fluff pulp, and 5 to 50% by weight of particulates of absorbent polymer. In this absorbent body, the heat-fusible crimped fibers are fusion-bonded to each other to have three-dimensional network structure, thereby improving the recovery (absorbency) and shape stability of the absorbent body.
However, in the invention disclosed in Japanese Unexamined Patent Publication No. 2-74254, the density of the three-dimensional framework composed of the heat-fusible fibers, the fluff pulp and the particulate absorbent polymer is high, which becomes a factor of interfering with one of basic functions in absorbent body i.e., swelling of the particulate absorbent polymer when body fluid is absorbed by the particulate polymer. In other words, there is a possibility of decreasing absorbency due to insufficient compressive recovery.
In addition, since the heat-fusible crimped fibers are thermally fusion-bonded to each other after the heat-fusible crimped fibers, the fluff pulp and the particulate absorbent polymer are mixed, the fluff pulp (not heat-fusible fibers) and the particulate absorbent polymer become an interfering factor. More specifically, fusion-bonding of the heat-fusible crimped fibers to each other in a condition where the fluff pulp (not heat-fusible fibers) and the particulate absorbent polymer are mixed therewith, requires large calorie. Here, if the processing temperature is simply set at a high level in order to increase the processing speed, the fusion-bonding can be done only in the surface of the absorbent body but not inside the absorbent body. As a result, sufficient shape stability can not be provided, so that the absorbent article may lose its shape after absorption of liquid. On the other hand, even if the heating rate is lowered, there is a problem of remarkable decrease in productivity, as well as it is still difficult to sufficiently heat inside of the absorbent body.